Process for preparing closed-cell water-blown rigid polyurethane foams having improved mechanical properties

ABSTRACT

The present invention is directed to a process for preparing water-blown rigid polyurethane foams having at least an 80% closed-cell content which involves reacting a) at least one polyol mixture which is composed of (i) at least one polymer polyol; (ii) at least one polyol having a hydroxyl value within the range of from about 200 to about 800; and (iii) optionally, at least one polyol having a hydroxyl value within the range of from about 25 to about 115; with b) at least one polymeric isocyanate and/or a prepolymer thereof; in the presence of c) optionally, at least one catalyst; d) water; and e) optionally, at least one additive or auxiliary agent. The present invention is also directed to the closed-cell water blown rigid polyurethane foams produced by the process of the present invention. The invention is further directed to a polyurethane-foam forming mixture which is used to produce the water-blown rigid polyurethane foams of the present invention. Foams produced according to the present invention have reduced friability and acceptable adhesion to substrates as well as acceptable compressive strength.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process for preparing closed-cellwater-blown rigid polyurethane foams which have reduced friability andacceptable adhesion to substrates and which also have acceptablecompressive strength. The present invention is also directed toclosed-cell water-blown rigid polyurethane foams produced by the processof the present invention. The invention is further directed to apolyurethane-foam forming mixture which is used to produce closed-cellwater-blown rigid polyurethane foams which have reduced friability andacceptable adhesion to substrates and which also have acceptablecompressive strength.

BACKGROUND OF THE INVENTION

Rigid polyurethane foams are widely known and are used in numerousindustries. Rigid polyurethane foams are produced by reacting apolyisocyanate with a polyol in the presence of a blowing agent.Chlorofluorocarbons (CFC's) were typically used as blowing agents toproduce rigid polyurethane foams which have excellent insulatingproperties. CFC's are now believed to contribute to the depletion ofozone in the stratosphere. As a result, mandates have been issued whichprohibit the use of CFC's.

Hydrogen-containing chlorofluorocarbons (HCFC's), hydrofluorocarboncompounds (HFC's) and mixtures of HCFC's and HFC's are blowing agentsconsidered to be acceptable alternatives to CFC's. HCFC 141b iscurrently used as an alternative to CFC's. However, due to the fact thatthe use of HCFC 141b will be phased-out beginning in 2003, effort hasbeen directed to using water as a blowing agent in the production ofsome rigid polyurethane foams.

There are, however, drawbacks to using water as a blowing agent forproducing rigid polyurethane foams. One such drawback is the fact thatfoams produced using relatively high levels of water as a blowing agentare friable and have relatively poor adhesion to substrates. See U.S.Pat. No. 5,013,766, column 1, lines 11-13.

A process for producing rigid polyurethane foams which are less brittleand which have acceptable adhesion to substrates has been investigated.For example, U.S. Pat. No. 5,013,766 describes a process for producingclosed-cell rigid polyurethane foams which are less friable and adherewell to substrates. The process disclosed in this patent focuses onreacting an isocyanate with a polyol mixture in the presence of acatalyst, water, trichlorofluoromethane (Freon 11) and a foamstabilizer. However, from the examples contained in U.S. Pat. No.5,013,766, one skilled in the art would recognize that foams produced bythe process described in this patent would have low compressivestrength.

Open-cell rigid polyurethane foams having acceptable compressivestrength which are produced using polymer polyols are known. Forexample, U.S. Pat. No. 6,127,443 discloses a process for producingopen-cell rigid energy absorbing polyurethane foams by reacting certainpolymer polyols with an isocyanate in the presence of a blowing agent(water) to generate rigid polyurethane foams in which the total polymersolids content of the foam is in excess of about 15 weight percent.Foams produced by the process described in this patent are designed forenergy management. Due to their open-cell structure, one skilled in theart would expect that the foams produced by the process described inU.S. Pat. No. 6,127,443 would have poor insulating properties. See W. A.Kaplan et al., Low-Density All Water-Blown Rigid Foam for Pour-in-PlaceApplications, Polyurethanes Expo '96 Conference Proceedings, pp. 179-89(1996) wherein it states that, unlike closed-cell water blownpolyurethane foams, open-cell polyurethane foams are poor insulators.

There therefore remains a need for closed-cell water-blown rigidpolyurethane foams which have reduced friability and acceptable adhesionto substrates but which also have acceptable compressive strength.

SUMMARY OF THE INVENTION

The present invention relates to a process for preparing closed-cellwater-blown rigid polyurethane foams which have reduced friability andacceptable adhesion to substrates and which also have acceptablecompressive strength. The present invention also relates to closed-cellwater-blown rigid polyurethane foams produced by the process of thepresent invention. The invention further relates to a polyurethane-foamforming mixture which is used to produce closed-cell water-blown rigidpolyurethane foams which have reduced friability and acceptable adhesionto substrates and which also have acceptable compressive strength.

DESCRIPTION OF THE INVENTION

The present invention is directed to a process for preparing water-blownrigid polyurethane foams having at least an 80% closed-cell contentwhich involves reacting a) at least one polyol mixture which is composedof i) at least one polymer polyol; ii) at least one polyol which has ahydroxyl value within the range of from about 200 to about 800; and iii)optionally, at least one polyol having a hydroxyl value within the rangeof from about 25 to about 115; with b) at least one polymeric isocyanateand/or a prepolymer thereof; in the presence of c) optionally, at leastone catalyst; d) water; and e) optionally, at least one additive orauxiliary agent.

The present invention is also directed to the closed-cell water blownrigid polyurethane foams produced by the process of the presentinvention. The invention is further directed to a polyurethane-foamforming mixture which is used to produce water-blown rigid polyurethanefoams having at least an 80% closed-cell content which is composed of a)at least one polyol mixture which is composed of i) at least one polymerpolyol; ii) at least one polyol which has a hydroxyl value within therange of from about 200 to about 800; and iii) optionally, at least onepolyol having a hydroxyl value within the range of from about 25 toabout 115; b) at least one polymeric isocyanate and/or a prepolymerthereof; c) optionally, at least one catalyst; d) water; and e)optionally, at least one additive or auxiliary agent.

Any polymer polyol known in the art can be used as component i) in thepolyol mixture of the present invention. Polymer polyols are dispersionsof polymer solids in a polyol. Polymer polyols which are useful in thepresent invention include the “PHD” polymer polyols as well as the “SAN”polymer polyols.

SAN polymer polyols are typically prepared by the in situ polymerizationof one or more vinyl monomers, preferably acrylonitrile and styrene, ina polyol, preferably, a polyether polyol, having aminor amount ofnatural or induced unsaturation. Methods for preparing SAN polymerpolyols are described in, for example, U.S. Pat. Nos. 3,304,273;3,383,351; 3,523,093; 3,652,639, 3,823,201; 4,104,236; 4,111,865;4,119,586; 4,125,505; 4,148,840 and 4,172,825; 4,524,157; 4,690,956;Re-28715; and Re-29118.

SAN polymer polyols useful in the present invention typically have apolymer solids content within the range of from about 10 to about 60 wt.%, preferably, from about 30 to about 45 wt. %, based on the totalweight of the SAN polymer polyol. As mentioned above, SAN polymerpolyols are typically prepared by the in situ polymerization of amixture of acrylonitrile and styrene in a polyol. When used, the ratioof styrene to acrylonitrile polymerized in situ in the polyol istypically in the range of from about 80:20 to about 0:100 parts byweight, based on the total weight of the styrene/acrylonitrile mixture.SAN polymer polyols useful in the present invention typically havehydroxyl values within the range of from about 15 to about 50,preferably, from about 20 to about 30.

Polyols used to prepare the SAN polymer polyols of the present inventionare typically triols based on propylene oxide, or mixtures of propyleneoxide and ethylene oxide. Alkoxylation of the starter can beaccomplished by using either propylene oxide, a mixture of propyleneoxide and ethylene oxide to form mixed block co-polymers, or by addingpropylene oxide followed by ethylene oxide to form an ethyleneoxide-capped polyol.

PHD polymer polyols are typically prepared by the in situ polymerizationof an isocyanate mixture with a diamine and/or hydrazine in a polyol,preferably, a polyether polyol. Methods for preparing PHD polymerpolyols are described in, for example, U.S. Pat. Nos. 4,089,835 and4,260,530.

PHD polymer polyols useful in the present invention typically have apolymer solids content within the range of from about 10 to about 30 wt.%, preferably, from about 15 to about 25 wt. %, based on the totalweight of the PHD polymer polyol. As mentioned above, PHD polymerpolyols of the present invention are typically prepared by the in situpolymerization of an isocyanate mixture, typically, a mixture which iscomposed of about 80 parts by weight, based on the total weight of theisocyanate mixture, of 2,4-toluene diisocyanate and about 20 parts byweight, based on the total weight of the isocyanate mixture, of2,6-toluene diisocyanate, with a diamine and/or hydrazine in a polyol,preferably, a polyether polyol.

PHD polymer polyols useful in the present invention typically havehydroxyl values within the range of from about 15 to about 40,preferably, from about 25 to about 35. Polyols used to prepare the PHDpolymer polyols of the present invention are typically triols based onpropylene oxide, ethylene oxide or mixtures thereof. Alkoxylation of thestarter is preferably accomplished with propylene oxide, followed by acap of ethylene oxide.

Any polyol known in the art which has a hydroxyl value within the rangeof from about 200 to about 800 can be used as component ii) in thepolyol mixture of the present invention. Examples of polyols useful ascomponent ii) include polyester polyols and polyether polyols havinghydroxyl values within the range of from about 200 to about 800.

Polyester polyols useful as component ii) in the present inventiontypically have an average functionality within the range of from about1.8 to about 8, preferably, from about 2 to about 6 and, morepreferably, from about 2 to about 2.5; hydroxyl number values within therange of from about 200 to about 800 mg KOH/g, preferably, from about200 to about 600 mg KOH/g.

Polyester polyols useful as component ii) in the polyol mixture of thepresent invention can be prepared by known procedures. Polyester polyolswhich are useful as component ii) in the present invention are typicallyobtained from polycarboxylic acids and polyhydric alcohols. Suitablepolycarboxylic acids which can be used in the present invention includeoxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,pimelic acid, suberic acid, azelaic acid, sebacic acid, brassylic acid,thapsic acid, maleic acid, fumaric acid, glutaconic acid, α-hydromuconicacid, β-hydromuconic acid, α-butyl-α-ethyl-glutaric acid, α-,β-diethylsuccinic acid, isophthalic acid, terephthalic acid, phthalicacid, hemimellitic acid and 1,4-cyclohexanedicarboxylic acid.Terephthalic acid is preferably used.

Suitable polyhydric alcohols which can be used to produce suitablepolyester polyols used as component ii) in the present invention includeethylene glycol, propylene glycol, dipropylene glycol, trimethyleneglycol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,7-heptanediol, hydroquinone, resorcinol, glycerine,1,1,1-trimethylol-propane, 1,1,1-trimethylolethane, pentaerythritol,1,2,6-hexanetriol, .alpha.-methyl glucoside, sucrose and sorbitol.Ethylene glycol is preferably used.

Any polyether polyol known in the art having a hydroxyl value within therange of from about 200 to about 800 mg KOH/g can be used as componentii) of the polyol mixture of the present invention. Polyether polyolswhich are useful as component ii) in the present invention typicallyhave an average functionality within the range of from about 1.8 toabout 8, preferably, from about 2 to about 6 and, more preferably, fromabout 2 to about 3.0; hydroxyl number values within the range of fromabout 200 to about 800 mg KOH/g, preferably, from about 200 to about 600mg KOH/g.

Polyether polyols which can be used as component ii) in the presentinvention can be prepared by known procedures such as by alkoxylatingstarter compounds. Any suitable alkylene oxide may be used such asethylene oxide, propylene oxide, butylene oxide, amylene oxide andmixtures of these oxides. Preferably, propylene oxide is used. Startercompounds which can be used in the present invention include, forexample, glycerine, trimethylolpropane, triethanolamine, ethanolamine,pentaerythritol, sucrose, sorbitol, propylene glycol, ethylene glycol,water and mixtures thereof. Preferably, glycerine is used.

Optionally, any polyol known in the art having a hydroxyl value withinthe range of from about 25 to about 115 mg KOH/g can be used ascomponent iii) in the polyol mixture of the present invention. Polyetherpolyols which are useful as component iii) in the present inventiontypically have an average functionality within the range of from about1.8 to about 3, preferably, from about 2 to about 3; hydroxyl numbervalues within the range of from about 25 to about 115 mg KOH/g,preferably, from about 40 to about 70 mg KOH/g.

Polyether polyols which can be used as component iii) in the presentinvention can be prepared by known procedures such as by alkoxylatingstarter compounds. Any suitable alkylene oxide may be used such asethylene oxide, propylene oxide, butylene oxide, amylene oxide andmixtures of these oxides. Preferably, mixtures of ethylene oxide andpropylene oxide are used. Starter compounds which can be used in thepresent invention include, for example, glycerine, trimethylolpropane,triethanolamine, ethanolamine, propylene glycol, ethylene glycol, waterand mixtures thereof. Preferably, mixtures of glycerine and propyleneglycol are used.

The amount of polymer polyol present in the polyol mixture of thepresent invention is typically in the range of from about 10 to about 80wt. %, preferably, from about 20 to about 60 wt. %, more preferably,from about 25 to about 40 wt. %, based on the total weight of the polyolmixture. The polyol mixture, catalyst (if used), water and additive orauxiliary agent (if used) are preferably combined to form anisocyanate-reactive mixture.

Optionally, any catalysts known in the art can be used in the presentinvention either alone or with one other catalyst or with multiplecatalysts. Examples of catalysts which can be used in the presentinvention include, for example, tin(II) salts of carboxylic acids;dialkyl tin salts of carboxylic acids; dialkyl tin mercaptides; dialkyltin dithioesters; bis-dimethylaminoethyl ethers; dimethyl benzylamines;tetramethylethylenediamine (TMEDA); dimethylaminodiglycols;dimethyldiglycolamines; sodium N-(2-hydroxy-5-nonyl phenyl)methyl-N-methylglycinate; and tertiary amines, such as, for example,dimethylcyclohexylamine.

Preferably, dimethyl benzylamine and tetramethylethylenediamine are bothused as catalysts in the present invention. If used, catalysts can bepresent in an amount within the range of from about 0.1 to about 5% byweight each, preferably, within the range of from about 0.1 to about2.0% by weight each, more preferably, within the range of from about 0.1to about 1.5% by weight each, based on the total weight of theisocyanate-reactive mixture.

Water is used as the blowing agent in the present invention. Although itis preferred to use water as the sole blowing agent in the presentinvention, auxiliary blowing agents, such as, for example, carbondioxide, can be used. Water can be used in an amount up to about 10% byweight. Preferably, about 1-8% by weight, more preferably, about 1-4% byweight, based on the total weight of the isocyanate-reactive mixture, ofwater is used in the present invention.

Optionally, any surfactants known in the art can be used in the presentinvention. Surfactants which can be used in the present inventioninclude polyether siloxanes. The structure of these compounds isgenerally such that a copolymer of ethylene oxide and propylene oxide isattached to a polydimethyl siloxane radical. Such foam stabilizers aredescribed in, for example, U.S. Pat. No. 2,764,565.

Preferably, silicon surfactants suitable for rigid polyurethane foamsare used in the present invention. Surfactants can be used in thepresent invention in amounts of from about 0.3 to about 3% by weight,preferably, in amounts of from about 0.5 to about 2% by weight, based onthe total weight of the isocyanate-reactive mixture. TEGOSTAB B 8421,which is available commercially from Goldschmidt AG, Essen, Germany, isan example of a surfactant which can be used in the present invention.

In addition to surface-active agents, other known additives can be usedin the present invention, including, for example, internal mold releaseagents; pigments; cell regulators; flame retarding agents; plasticizers;dyes; and fillers, all of which are known in the art. Known reinforcingagents such as, for example, glass in the form of fibers or flakes orcarbon fibers can also be used.

Any polymeric isocyanates and/or prepolymers thereof can be used in thepresent invention. Preferably, polymeric isocyanates and/or prepolymersthereof which are used in the present invention include, for example,polymeric diphenylmethane diisocyanates having an NCO group contentwithin the range of from about 25 to about 33%, an average functionalitywithin the range of from about 2.5 to about 3.0 and a viscosity withinthe range of from about 50 to about 1,000, preferably, from about 150 toabout 800 mPa·s at 25° C.

Polymeric isocyanates and/or prepolymers thereof useful in the presentinvention are typically used in an amount such that the isocyanate indexis within the range of from about 100 to about 150, preferably, withinthe range of from about 120 to about 140. The term “Isocyanate Index”(also commonly referred to as “NCO index”), is defined herein as thequotient of the number of equivalents of isocyanate divided by the totalequivalents of isocyanate-reactive hydrogen containing materials,multiplied by 100. When water is present as the blowing agent, thequantity of water present is considered in calculating the isocyanateindex.

The present invention is also directed to closed-cell water-blown rigidpolyurethane foams produced according to the present invention.Closed-cell water-blown rigid polyurethane foams of the presentinvention have reduced friability and acceptable adhesion to substratesand relatively high compressive strength. Solids from the polymer polyolare typically present in the closed-cell water-blown rigid polyurethanefoams produced according to the present invention in an amount fromabout 1 to about 30 wt. %, based on the total weight of the foam.

The compressive strength of the closed-cell water-blown rigidpolyurethane foams produced according to the present invention istypically in the range of from about 35 to about 150 lb/in². Foamsproduced according to the present invention have acceptable insulatingproperties. For insulating foams, the object is to retain the blowingagent in the cells to maintain a low k-factor. “K-factor” is ameasurement of the thermal conductivity of the insulating material,i.e., the rigid polyurethane foam. Thus, less open-cell content in thefoam is desirable. Foams produced according to the present inventiontypically have more than an 80% closed-cell content.

Foams produced according the invention have acceptable adhesion tosubstrates. The adhesive properties of water-blown rigid polyurethanefoams are determined by measuring tensile adhesion strength of the foamto a desired substrate. ASTM D-1623 is an acceptable standard formeasuring tensile adhesion of water-blown rigid polyurethane foams.Preferably, water-blown rigid polyurethane foams produced according tothe present invention have a tensile adhesion strength greater than 60lbs/in² as measured by ASTM D-1623 when adhered to an aluminum or to anacrylonitrile/butadiene/styrene (ABS) substrate.

Foams produced according to the present invention are particularlyuseful in applications such as, for example, foam-filling items such aspicnic coolers, vending machines, entry or garage doors, water heaters,flotation devices and sandwich composites for trailer side-walls(non-refrigerated).

The following examples merely illustrate the invention. Those skilled inthe art will recognize many variations that are within the spirit of theinvention and scope of the claims.

EXAMPLES

The following compounds were used in the examples:

-   Polyol A: a polyether polyol having an OH number of about 56    prepared by KOH-catalyzed alkoxylation of a mixture of    gycerine:propylene glycol (88:12 pbw) with a block of propylene    oxide (30 wt. % of the total oxide), followed by a mixed block of    propylene oxide (40 wt. % of the total oxide) and ethylene oxide (10    wt. % of the total oxide) and finished with a block of propylene    oxide (20 wt. % of the total oxide);-   Polyol B: a polyether polyol having an OH number of about 470    prepared by KOH-catalyzed alkoxylation of glycerine with propylene    oxide;-   Polyol C: a polyether polyol having an OH number of about 56    prepared by zinc hexacyanocobaltate-catalyzed alkoxylation of a    mixture of glycerine:propylene glycol (86:14 pbw) with a mixed block    of propylene oxide (93 wt. %) and ethylene oxide (7 wt. %);-   Polyol D: a modified diethylene glycol phthalate polyester polyol    having an OH value of from about 230 to about 250 which is    commercially available as STEPANPOL PS 2502 A from Stepan Company,    Northfield, Ill.;-   Polymer Polyol A: a 20 weight % solids polymer polyol having an OH    10 number of about 29, in which the solids are the reaction product    of an 80:20 pbw mixture of 2,4- and 2,6-toluene diisocyanate and    hydrazine polymerized in situ in a base polyol which is a    KOH-catalyzed glycerine initiated propylene oxide triol with a 17    wt. % ethylene oxide cap, having an OH number of about 35;-   Polymer Polyol B: a 45 weight % solids polymer polyol having an OH    number of about 28 in which the solids are a styrene/acrylonitrile    (63:37 pbw) mixture polymerized in situ in a base polyol which is a    KOH-catalyzed glycerine initiated propylene oxide/ethylene oxide    (87.5:12.5 pbw) triol having an OH number of about 53;-   Polymer Polyol C: 43 weight % solids polymer polyol having an OH    number of about 20 in which the solids are a styrene/acrylonitrile    (63:37 pbw) mixture polymerized in situ in a base polyol which is a    KOH-catalyzed glycerine initiated propylene oxide triol with a 20    wt. % ethylene oxide cap, having an OH number of about 36;-   Catalyst A: dimethyl benzylamine;-   Catalyst B: tetramethylethylene diamine;-   Surfactant A: TEGOSTAB B 8421, which is available commercially from    Goldschmidt AG, Essen, Germany;-   Isocyanate A: a polymeric diphenylmethane diisocyanate having an NCO    group content of about 31.5%, a functionality of about 2.8 and a    viscosity of about 200 mPa·s at 25° C.; and-   Isocyanate B: an isocyanate terminated prepolymer prepared from    Isocyanate A and Polyol D having an NCO content of about 29.4%, a    molecular weight of about 400 g/mole and a functionality of about    2.8.

For each of the Examples 1-5, a 14″×14″×1″ clamped aluminum mold washeated to 40° C. The polyol, polymer polyol (if present), water,surfactant and catalyst were hand-mixed to form an isocyanate-reactivemixture. The isocyanate as well as the isocyanate-reactive mixture wereallowed to equilibrate to 20° C. The isocyanate-reactive mixture wascombined with the isocyanate and mixed with a conventional motor-drivenstirrer at 2800 rpm for ten seconds. The reactive mixture was thenpoured into the aluminum mold. The mold was first left open at the topand over-filled to determine minimum fill density by cutting the sampledown to known dimensions and determining the mass. After the minimumfill density was determined, the mold was clamped closed and packed to adensity of 15% over the minimum fill density. The foam was sandwichedbetween one galvanized aluminum facer and one aluminum facer. The facerswere fixed in the mold during foaming using vinyl tape to prevent foamfrom flowing between the facers and the mold surface. Foams were held inthe clamped fixture at 40° C. for 20 minutes before de-molding. Theformulations used in Examples 1-5 are set forth in Table 1. Themechanical properties of the foams produced using the formulations ofExamples 1-5 are set forth in Table 2.

As illustrated in Table 2, the foams produced with the formulations ofExamples 1-4 had relatively high compressive strength and tensileadhesion. Also, as illustrated in Table 2, the formulation of Example 5(a comparative example), which did not contain polymer polyol, produceda foam which had a relatively low compressive strength compared to thefoams of relatively the same density produced with the polymerpolyol-containing formulations of Examples 14.

For each of the Examples 6-7, a 14″×14″×2¾″ clamped aluminum mold washeated to 40° C. The polyol, polymer polyol (if present), water,surfactant and catalyst were hand-mixed to form an isocyanate-reactivemixture. The isocyanate as well as the isocyanate-reactive mixture wereallowed to equilibrate to 20° C. The isocyanate-reactive mixture wascombined with the isocyanate and mixed with a conventional motor-drivenstirrer at 2800 rpm for ten seconds. The reactive mixture was thenpqured into the aluminum mold. The mold was first left open at the topand over-filled to determine minimum fill density by cutting the sampledown to known dimensions and determining the mass. After the minimumfill density was determined, the mold was clamped closed and packed to adensity of 15% over the minimum fill density. The foam was sandwichedbetween two ABS facers. The ABS facers were fixed in the mold duringfoaming using vinyl tape to prevent foam from flowing between the facersand the mold surface. Foams were held in the clamped fixture at 40° C.for 20 minutes before de-molding. The formulations used in Examples 6-7are set forth in Table 3. The mechanical properties of the foamsproduced using the formulations of Examples 6-7 are set forth in Table4.

As illustrated in Table 4, the foam produced according to theformulation of Example 6 had relatively high compressive strength andtensile adhesion. Also, as illustrated in Table 4, the formulation ofExample 7 (a comparative example), which did not contain polymer polyol,produced a foam which had a low compressive strength compared to thefoam of relatively the same density produced with the polymerpolyol-containing formulation of Example 6.

The foams produced in the foregoing examples were tested according tothe following test methods:

-   -   Molded Density: ASTM D-1622    -   Compressive Strength: ASTM D-1621

Tensile Adhesion: ASTM D-1623 (Type C specimen) TABLE 1 Example 1 2 3 45* Polyol B 37.6 g 37.6 g 37.6 g 37.6 g 37.6 g Polyol C 28.2 g 56.4 gPolymer 56.4 g Polyol A Polymer 56.4 g 28.2 g Polyol B Polymer 56.4 gPolyol C Catalyst A 1.40 g 1.40 g 1.40 g 1.40 g 1.40 g Catalyst B 0.14 g0.14 g 0.14 g 0.14 g 0.14 g Surfactant A 1.44 g 1.44 g 1.44 g 1.44 g1.44 g Water 2.5 g 2.5 g 2.5 g 2.5 g 2.5 g Isocyanate A 110.8 g 109.4 g111.0 g 113.3 g 115.8 g*Comparative Example

TABLE 2 Example 1 2 3 4 5* Density (lbs/ft³) 5.70 5.66 5.73 5.75 5.69Compressive 86 84 69 79 62 strength (perpendicular) (lbs/in²) TensileAdhesion 126 123 109 121 105 (lbs/in²) Closed-cell 85 86 84 84 84 (%)Solids in foam 12.1 11.6 5.4 6.0 0 (wt. %)*Comparative Example

TABLE 3 Example 6 7* Polyol A  56.4 g Polyol B  37.6 g  37.6 g PolymerPolyol B  56.4 g Catalyst A  1.40 g  1.40 g Catalyst B  0.14 g  0.14 gSurfactant A  1.44 g  1.44 g Water  3.0 g  3.0 g Isocyanate B 131.9 g137.2 g*Comparative Example

TABLE 4 Example 6 7* Density (lbs/ft³) 3.23 3.28 Compressive 44 24strength (perpendicular) (lbs/in²) Tensile Adhesion 73 75 (lbs/in²)Closed-cell 86 84 (%) Solids in foam 10.9 0 (wt. %)*Comparative Example

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

1-12. (Cancelled).
 13. A polyurethane-foam forming mixture comprising:(a) at least one polyol mixture comprising: (i) at least one polymerpolyol; (ii) at least one polyol having a hydroxyl value within therange of from about 200 to about 800; and (iii) optionally, at least onepolyol having a hydroxyl value within the range of from about 25 toabout 1 15; (b) at least one polymeric isocyanate and/or a prepolymerthereof; (c) optionally, at least one catalyst; (d) water; and (e)optionally, at least one additive or auxiliary agent wherein foam madefrom the mixture has a perpendicular compressive strength within therange of from about 35 to about 105 lbs/in² and a tensile adhesiongreater than 105 lbs/in².
 14. The mixture of claim 13 in which polymerpolyol (i) is comprised of at least one solid which is the reactionproduct of a mixture of 2,4- and 2,6-toluene diisocyanate and hydrazinepolymerized in situ in a polyether polyol.
 15. The mixture of claim 13in which polymer polyol (i) is comprised of at least one solid which isa styrene/acrylonitrile mixture polymerized in situ in a polyetherpolyol.
 16. The mixture of claim 13 in which polymer polyol (i) has fromabout 10 to about 60 weight percent, based on the total weight of thepolymer polyol, of at least one polymer solid as a dispersed phase. 17.A rigid polyurethane foam produced with the polyurethane-foam formingmixture of claim
 13. 18. The mixture of claim 13, wherein the foam has adensity within the range of from about 5.66 to about 5.75 lbs/ft³ and aclosed-cell content of at least 80%.
 19. The mixture of claim 13,wherein the foam has a density of about 3.23 lbs/ft³ and a closed-cellcontent of at least 80%.